Method of treating armor-plates.



UNITED STATES PATENT OFFICE.

SAMUEL S. WALES, OF MUNHALL, PENNSYLVANIA.

METHOD CF TREATDQ' G ARMOR-PLATES,

To all whom it may concern:

Be it known that I, SAMUEL S. WALES, of Munhall, Allegheny county, Pennsylvania, have invented a new and useful Method of Treatin Armor-Plates, of which the following 1s a full, clear, and exact description.

My invention relates to the manufacture of face-hardened armor plates, and more particularly to the steps of heating and quenching for final water-hardening. In my pending application for Patent, Serial No. 401,702,filed November 11th, 1907, I have described and claimed a novel method of this character for treating armor plate, which consists in heating that face of the plate which is to be hardened to a hardening tom erature and simultaneously cooling the bacli of the plate by forcing a cooling fluid upon it for the purpose of maintaining the back in the condition in which it was left by its immediately preceding metallurgical treatment, then chilling in any approved way, and whereby I produce a face-hardened plate having three layers, namely, a faceiardened layer, a back portion, and a relatively thin intermediate layer of annealed material. This intermediate layer occurs at the point or zone where the temperature changes from the water-l1ardening range to the temperature Where no action takes. place in quenching. i

My present invention relates more particularly to the control of the position of this relatively thin intermediate layer of annealed material with respect to the faces of the plate, and also to the control of the thickness of fills intermediate layer itself. It is obvious t at the control of the position of this intermediate layer is of great importance, since such position controls the thickness of the face-hardened portion 01- layer of the plate; and it is also important to control the thickness of the intermediate layer itself within such limits that it will not impair to any material extent the strength of the back of the plate.

I, have found that the position of this intermediate layer may be varied by varying the length of time during which the cooling fluid is applied to the back of the plate, and that the thickness of the layer may be controlled by varying the duration of the interval during which the cooling fluid is supplied. That is to say, by alternately applyingthe cooling fluid to and cutting itofi from the back ofthe plate and by varying Specification of Letters Patent.

Application filed March 27, 1908, Serial N 0. 423,525.

PatentedJuly, 20, 1909.

Renewed December 6, 1903. Serial No. 466,165.

the ratio of the time during which the water is applied to the time during which it is cut off, and by also varying the duration of the interval during which the water is alternately applied and cut off, the position and thickness of this layer can be controlled. within certain more or less exact limits.

In carrying out my invention, the face to be hardened is exposed in the furnace, directly to the heat, while the edges are protected by any convenient refractory material so as to force the heat to penetrate from the front surface only. At the same timethe back is exposed to a positive cooling action such as a spray of water, steam, or other cooling fluid, which isforced against it. The application of this cooling fluid isinterrupted at intervals, both the frequency of the interruptions, and the length of each interruption, depending upon the result which it is desired to produce, as hereinafter more fully explained. The effect of inter rupting or cutting off this cooling fluid is to cause the heat during the interval of the interruption to penetrate deeper into the plate, or to gain relatively upon the cooled back portion; and when the cooling fluid is again applied, some of this heat is extracted, or in other words, the penetration of the heating is temporarily arrested and the back is again cooled down.

As hereinafter stated, I have found and the position of the intermediate layer in any particular plate will depend largely upon the ratio between the total time during which the cooling fluid is applied and the total time during which such fluid is 1nterrupted. That is, the greater the total time of application of the cooling fluid relatively to the total time of its interruption, within certain limits, the thinner will be the hard face of the plate and the thicker its back portion. Therefore, to increase the depth of the hard face, the proportion of the time during which the water is applied that the relative thickness of the chilled portion should bediminished, and if it is desired to decrease the thickness of the hard face, the greater will be the proportion of time during which the cooling fluid isapplied, Thus, with a plate which is six inches in thickness I have found that when the coolingfltud is applied during the entire. time of treatment, a chilled portion of a thlckness of from about a uarter to one half inch may be produced, w ile by applying the cooling fluid only during twenty per cent. of the to materially ing fluid was applied during intervals of one-half of a minute each and was cut off for intervals of two minutes each, the thickness of this layer. was from three-quarters of an inch to one inch, but when the intervals of application of the cooling fluid were increased to two and one-half mmutes each, and the intervals of interruption to ten minutes each (which intervals it will be seen bear the same ratio to each other as in the first case) ,the thickness of the intermediate layer increased to approximately two and one-half inches. I

In carrying out my process, the furnace is preferably heated at the start to a temperature of between ten hundred and twelve hun dred degrees (3., and the treatment may be required to continue for a period equivalent to 25 to 35 minutes for each inch thicknessv of plate. The surface of the plate should be eated' preferably from 850 to 950 (1., and in some cases it may be necessary to increase the time of' treatment for each inch of plate sufliciently to reach these temperatures. The back is maintained by the application of the cooling fluid at a temperature such that no annealing can take place, and depending somewhat upon its previous metallurgical treatment. The late is then removed from the furnace an water-quenched in the usual manner, as, for example, by spraying one or both faces of the plate wit water. In this water-quenching the heated face of the plate receives its final hardness,

while the back of the plateis not materially changed in its characteristics, on account of having been maintained at a much lower temperature than that of its final toughening treatment.

- When a plate which has been treated ac cording to my method is withdrawn from the furnace and chilled, it will be found to contain three different layers or zones, there being a strong back portion which maintains the characteristics imparted thereto by the last metallurgical treatment previous to heating for hardening, owin' to the fact that the cooling of the back 0 the plate has prevented its temperature being raised to a point where any annealing can take place either during the'heating process or during the subsequent quenching; a face-hardened portion in which the hardness is substantially uniform by reason of the uniformity of temeratur'e therein, and by reason of the heatmg being practically limited to this portion of the p ate, so that the total heat to be extracted is relatively small; and a relatively thin intermediate ayer where the temperature chan es from the water-hardening range to t e temperature where no action takes lace in quenching, and the position and thickness of which will depend upon the mode or manner of application and interruption of the cooling fluid in the manner above described,

While as above stated, I ma use either water, steam, air or other coo ing fluid, I have found the best results to be obtained by the use of water.

The fracture of a plate which has been treated in accordance with my invention may show three distinctly visible layers or strata corresponding to the three zones or layers above described. In some cases the division line between the middle layer and the main body or back of the plate may-not be distinctly visible to theeye wherethe main body or back of the plate'was annealed to the same condition before heating for water-hardening, as this strip will be after the process of heating for water-hardening.

In case the body or back of the plate has My present invention, while producing a plate having all the advantages described 1n my said application, has-the added advantage of enabling me to control within very close limits the location and thick ness of the intermediate zone or layer by controlling the two factors which determine the thickness and position of this layer, viz., the total time of application ofthe cooling fluid relatively to the total time of the interruption of the same, and the actual duration of the intervals of application and interruption, as described.

It will be understood that the thicker the plate to be treated the reater should be the total time during which the coolin fluid is applied, and that in order to keep t e thickness of the intermediate layer or zone within the desired limits, the actual time of each interruption of the cooling fluid should be short. In practice I have found that each interval of interruption should not be more than five minutes in length, and I prefer that they shall not iexceed three minutes, although I do not of course limit myself to intervals of interruption of any. definite length, since these will vary quite largely with the thickness of the plate and other conditions peculiar to each case.

My invention is of more particular ad vantage in connection with relatively thin plates, since with plates of a thickness of 12 inches or over, it will usually be preferable to maintain the cooling action'on the back of the plate during substantially the entire period of treatment, as described in my said application.

I have herein stated that the face portion or layer of the plate will be of substantially uniform hardness throughout. This ap plies, however, only to plates which have not been face carburized previously to being 7 treated as herein described, and in which the greater hardness of the extreme face isdue to the increased carbon thereof and not to my method of treatment.

I claim 2-- 1. In the manufacture of face-hardened armor plate, the step which consists in heating that face of the plate which is to be hardened to a hardening temperature, simultaneously artificially cooling the back of the plate, and periodically interrupting the cooling action or efiect; substantially as describe 1 2. In the manufacture of face-hardened armor plate, the step which consists in heat ing that face of the plate which is to be hardened to a hardening temperature, simultaneously artificially cooling the back of the plate, periodically interrupting the cooling action or effect, and controlling the length of each period of interruption; substantially as described.

3. In the manufacture of face-hardened armor plate, the method of treatment which consists in heating one face of the plate to a hardening temperature and simultaneously applying a cooling medium to the opposite face, interrupting such application periodically, and making the intervals of interruption and of application of the coolin' medium of'diflerent lengths; substantia ly as described.

4. In the manufacture of face-hardened armor plate, the method of treatment which consists in heating one face of the plate to a hardening temperature and simultaneously to produce a plate havin portion or layer, a strong ack ortion, and

an intermediate relatively thin ayer of anapplying a cooling medium to the opposite face, interrupting periodicallythe application of said medium, and controlling both the total time of interruption and of application of said medium relatively to each other and also controlling'the length of each interval of interruption with respect to the length of the intervals of application; substantially as described.

5. In the manufacture of face-hardened armor plate, the method of treatment which consists in heating one face of the plate to a hardening temperature and ap lyin a cooling medium to the opposite ace uring a portion only of the time of heating; substantially as described.

6. In the method of treatin armor plate to produce a plate having a face-hardened portion or layer, a strong back ortion, and an intermediate relativelythin ayer of annealed material, the step which consists in applying a hardening temperature to one face of a plate, and simultaneously intermittently applying a cooling medium to the opposite face, and regulating the position of the intermediate layer by controlling the total time of interruption of the application of said medium relatively to the total time of its application; substantially as described.

7. In the method of treatin armor plate a ace-hardened nealed material, the step which consists in applying a hardening temperature to one face of a plate, and simultaneously intermittently applyin a cooling mediumto the opposite face, an regulatingthe thickness of the intermediate layer by controlling the length of the intervals of interruption; sub stantially as described.

8. In the method of treating armor plate,

the step which consists in cooling one face portion of the plate, and simultaneously applying a hardening temperatureto the opposite face portion, and interrupting the cool ing action at substantially regular intervals and for a substantially definite len th of time at each interval; substantia ly as described. 7

In testimony whereof, I have hereunto set my hand.

SAMUEL S. WALES.

Witnesses:

D. A. HAMILTON, W. CORBETT. 

